PURPOSE: To obtain a sound formed body having little dispersion of content of oxygen even if sharp temp. difference is developed in preform treated body at the time of raising the temp. with hydraulic press HIP treatment by executing the hot isostatic pressurizing treatment after executing soaking treatment to the preform treated body at the specific temp. for the necessary time.

CONSTITUTION: Metal powder is packed in a capsule and the sealed preform treated body 1 is heated for the necessary time, and after soaking, this is charged in a pressure vessel 8 and the hot isostatic pressing treatment is executed to this by using liquid having good fluidity or viscous plastic body as pressure medium 7. In this case, after executing soaking treatment to the preform treated body 1 at ≤1,000°C for the necessary time, the hot isostatic pressurizing treatment is executed. Therefore, as the HIP forming temp. is less than the temp. generating CO2 gas, CO2 gas is not generated and also as any oxide is not generated at low temp. part, even if quick part and delay part of the temp. raising are developed at the time of heating the preform treated body 1, the oxygen content in the HIP formed body is not largely different among the measured positions and the dispersion of the oxygen content in the formed body is almost eliminated.